The present invention relates in general to downhole electrical connectors for use in oil field applications, and in particular to a downhole pothead connector for connecting a motor lead to an electrical motor of a submersible pump assembly.
Electric submersible pumps have been used in oil wells to pump well fluids for many years. These types of prior art submersible pumps include electrical connectors for connecting the electric motors of the pumps to electrical conductors of downhole cables. These pumps are often used in corrosive environments such as wells that produce sour gas, and hydrogen sulfide (H2S).
Electrical connectors for electric submersible pumps typically have elastomeric seals or pothead connectors. The hydrogen sulfide encountered in sour gas wells will permeate elastomeric seal materials and deteriorate these seals. This allows the gas to migrate back into the electrical connectors, corroding the connectors and seriously reducing the service life of downhole pothead connectors and pumps.
A separate problem encountered with pothead connections is the movement of conductors within the connector during installation and/or handling. The result of this movement is shear stress damage to the cable insulation and the insulation within the connector itself, either of which is likely lead to the failure of the electrical connection.
A pothead connector for use with an electric submersible pump is provided to connect a downhole cable to an electrical motor of the submersible pump.
The pothead connector has a tubular housing having an rearward end and a forward end. The downhole cable has electrical conductors that are separately covered by insulation layers. In the embodiment shown, lead sheaths separately extend around each of the insulation layers to encase and protect each of the electrical conductors. The downhole cable extends through the rearward end and into the tubular housing, and then is electrically connected to the electric motor through the forward end of the tubular housing.
An insulating block is provided in the forward end of the tubular housing for separating and holding the electrical conductors in alignment and to prevent movement of the conductors within the housing. A bore is provided through the insulating block for each of the conductors. The bore is provided with an annular shoulder for abutting against a flange that radially extends from a conductor pin and is further provided with threads for engaging with an insulating sleeve.
A conductor pin is provided that is at least partially inserted into the bore of the insulating block and is fixed to the terminal end of the conductor. The conductor pin also has an opening for receiving an electrical lead from a downhole pump motor. An insulating sleeve is provided having a bore which is configured to slide over the conductor pin and abut against the flange of the conductor pin urging the pin against the annular shoulder within the insulating block. The insulating sleeve is further provided with external threads for engaging with the threads of the insulating block when the sleeve is inserted into the bore of the insulating block.
In the embodiment shown, a lead based alloy solder seal disc is disposed within the tubular housing, intermediately between the rearward and forward ends. The solder seal extends between and is wetted to the protective lead sheaths and an interior perimeter of the tubular housing to seal therebetween. The seal disc is alloyed so as to have substantially no contraction as it cools and solidifies. An epoxy layer extends between the cable and the interior perimeter of the tubular housing, adjacent to an rearward end of the lead based seal disc. A second epoxy layer is disposed within the tubular housing on a forward side of the lead based alloy seal, opposite from the rearward side. Fasteners secure the tubular housing to the electric motor.